U.S. Fish & Wildlife Service Desert Bighorn Sheep Kofa National Wildlife Refuge

Kofa National Wildlife Refuge’s Desert Bighorn Sheep To many of our visitors, the desert bighorn sheep is the epitome of Kofa National Wildlife Refuge’s desert wilderness. Bighorn are a true sheep distantly related to domestic sheep. The name “desert bighorn sheep” applies to those bighorn inhabiting hot and dry mountain ranges with sparse vegetation. Biologists recognize four desert bighorn sheep subspecies, including the Mexican bighorn sheep (Ovis canadensis mexicana) which is found on the refuge.

Characteristics Desert bighorn are stocky, heavy- bodied sheep, similar in size to mule deer. Weights of mature rams (males) range from 125 to 200 pounds, while ewes (females) are somewhat smaller. Due to their unique padded hooves, bighorn are able to climb the steep, rocky desert mountains with speed and agility. Bighorn rely on their keen eyesight to detect potential predators and use their Desert bighorn at Kofa National Wildlife Refuge. / © Illustration by Elizabeth Montgomery climbing ability to escape.

Both sexes develop horns soon after Unlike most mammals, desert bighorn (usually July-October), though breeding birth with horn growth continuing sheep have the ability to lose up to 30% may occur anytime in the desert due to throughout their lifetimes. Older rams of their body weight in water (more suitable climatic conditions. have impressive sets of curling horns than a camel) and still survive. Bighorn measuring over three feet long with a may go without drinking for weeks or Rams battle to determine the dominant circumference of more than a foot at the months during the cooler parts of the animal. They face each other and charge base. The head and horns of an adult year, although lactating ewes need water head-on from distances of twenty feet ram may weigh more than 30 pounds. more often. During the hot, dry summer or more, crashing their massive horns The ewes’ horns are much smaller and months, bighorn often go three to seven together with tremendous impact until lighter and do not tend to curl. Both rams days without drinking, sustaining their one animal ceases. The winning males are and ewes use their horns for fighting body moisture from their food alone. able to breed with the ewes. and as tools to remove the spines from After drinking up to two gallons of water and break open cacti, which they then in just a few minutes, they recover from Gestation lasts about six months and the consume. Desert bighorn sheep live to be their dehydrated condition. lambs are typically born in late winter. between 10 and 20 years old. Their age is indicated by annual growth rings in Food Historic Population Declines and the horns. Bighorn feed on a wide variety of leaves, Conservation twigs, flowers, forbs, grasses, and cacti. In the early 1900s, desert bighorn Desert Adaptations On Kofa National Wildlife Refuge, plants populations gradually declined. Desert bighorn sheep are well-adapted to that bighorn are known to forage include Competition from introduced animals the climate of the Sonoran Desert. They ironwood, palo verde, jojoba, Mormon and human activities were primarily are able to survive the extreme heat of tea, brittlebush, and barrel cactus. responsible for the population decrease. summer and the cold of winter because Domestic cattle and sheep, as well as their body temperature can safely Social Life feral horses and burros, compete with fluctuate several degrees. Bighorn also Mature bighorn live in separate ram bighorn, especially at water sources. escape the heat by resting in the shade of and ewe bands most of the year. They Native herbivores, like the mule deer, do trees and caves during the day. gather together during breeding season not generally adversely affect bighorn. Domestic stock also introduced diseases Gale Monson and Lowell Sommer, editors, The Desert Bighorn, Its Life History, Ecology, and Management, University of Arizona Press, 1990.

Gary P. Nabhan, editor, Counting Sheep, 20 Ways of Seeing Desert Bighorn, University of Arizona Press, 1993.

Charles Sheldon, The Wilderness of Desert Bighorns and Seri Indians, from the Southwestern Journals of Charles Sheldon, The Arizona Desert Bighorn Sheep Society, Inc. 1979

For More Information Contact: U.S. Fish and Wildlife Service Kofa National Wildlife Refuge 9300 East 28th Street Yuma, AZ 85365 928/783-7861 Monday–Friday: 8:00 a.m.–4:30 p.m. to bighorn populations. Kofa National Kofa NWR Bighorn Conservation February 2014 Wildlife Refuge’s bighorn, like other The number of desert bighorn sheep Arizona bighorn, suffer occasionally from estimated to be on Kofa National Wildlife chronic sinusitis (caused by a bot fly) Refuge declined from over 800 animals in which may ultimately be fatal. 2000 to less than 400 in 2006. Subsequent surveys from 2007 to 2012 showed little Human activities influencing bighorn increase has since taken place. As a numbers include habitat loss from result, transplants of bighorn sheep development and habitat encroachment, from Kofa National Wildlife Refuge were such as roads, fences, canals, mining, suspended in 2005. The U.S. Fish and and military and recreational activities. Wildlife Service, working closely with Individual bands and eventually whole the Arizona Game and Fish Department, populations have been lost as useable has undertaken an effort to increase the habitat decreases. number of bighorn by investigating the causes of mortality, controlling predation Conservation efforts beginning in of bighorn, maintaining permanent water the 1930s have resulted in population sources in critical locations, reducing increases and the restoration of desert the number of hunting permits issued bighorn sheep into historic habitat. annually, and identifying lambing areas Bighorn are found today in many parts that may potentially be closed to human of their historic range, including Arizona, entry during the peak of lambing season. California, Nevada, Utah, New Mexico, Texas, Baja California, and Sonora. Kofa Suggested Reading List and Cabeza Prieta National Wildlife Aldo Leopold, “A Plea for Wilderness Refuges in Arizona, Desert National Hunting Grounds,” Outdoor Life, Wildlife Refuge in Nevada, and San November, 1925. Andres National Wildlife Refuge in New Mexico are all federally established areas Bill Hook and Raymond Lee, editors, for the conservation of desert bighorn, Borrego, The Fall and Rise of Desert Desert bighorn. / All Photographs USFWS among other wildlife. Bighorn Sheep in Arizona, The Arizona Desert Bighorn Sheep Society, Inc, 1987. The reintroduction of bighorn to parts of their historic range is accomplished William T. Hornaday, Campfires on by capturing bighorn sheep in healthy, Desert and Lava (reprinted Tucson: thriving populations and transporting University of Arizona Press, 1985). them to a new location. Transplant funding comes from donations from the Raymond M. Lee, editor, The Desert Arizona Desert Bighorn Sheep Society Bighorn Sheep in Arizona, Arizona Game and proceeds from the sale and auction of and Fish Department, 1989. special bighorn sheep hunting permits. Karl Lumholtz, New Trails in Mexico (reprinted Glorieta: Rio Grande Press, 1971).